From 295e7c80e88e7fabad278cf7eacabf5a50d329b3 Mon Sep 17 00:00:00 2001
From: Tony Finch <fanf@isc.org>
Date: Fri, 3 Mar 2023 12:01:03 +0000
Subject: [PATCH] Ad-hoc backtrace logging with isc_backtrace_log()

It's sometimes helpful to get a quick idea of the call stack when
debugging. This change factors out the backtrace logging from named's
fatal error handler so that it's easy to use in other places too.
---
 bin/named/main.c                | 30 ++++--------------------------
 lib/isc/assertions.c            |  4 ++--
 lib/isc/backtrace.c             | 30 ++++++++++++++++++++++++++++++
 lib/isc/include/isc/backtrace.h | 14 ++++++++++++++
 4 files changed, 50 insertions(+), 28 deletions(-)

diff --git a/bin/named/main.c b/bin/named/main.c
index 752745d7fe..9ae8832a40 100644
--- a/bin/named/main.c
+++ b/bin/named/main.c
@@ -101,13 +101,6 @@
  */
 /* #include "xxdb.h" */
 
-/*
- * The maximum number of stack frames to dump on assertion failure.
- */
-#ifndef BACKTRACE_MAXFRAME
-#define BACKTRACE_MAXFRAME 128
-#endif /* ifndef BACKTRACE_MAXFRAME */
-
 extern unsigned int dns_zone_mkey_hour;
 extern unsigned int dns_zone_mkey_day;
 extern unsigned int dns_zone_mkey_month;
@@ -189,9 +182,6 @@ assertion_failed(const char *file, int line, isc_assertiontype_t type,
 static void
 assertion_failed(const char *file, int line, isc_assertiontype_t type,
 		 const char *cond) {
-	void *tracebuf[BACKTRACE_MAXFRAME];
-	int nframes;
-
 	/*
 	 * Handle assertion failures.
 	 */
@@ -203,24 +193,12 @@ assertion_failed(const char *file, int line, isc_assertiontype_t type,
 		 */
 		isc_assertion_setcallback(NULL);
 
-		nframes = isc_backtrace(tracebuf, BACKTRACE_MAXFRAME);
 		isc_log_write(named_g_lctx, NAMED_LOGCATEGORY_GENERAL,
 			      NAMED_LOGMODULE_MAIN, ISC_LOG_CRITICAL,
-			      "%s:%d: %s(%s) failed%s", file, line,
-			      isc_assertion_typetotext(type), cond,
-			      (nframes > 0) ? ", back trace" : "");
-		if (nframes > 0) {
-			char **strs = isc_backtrace_symbols(tracebuf, nframes);
-			if (strs != NULL) {
-				for (int i = 0; i < nframes; i++) {
-					isc_log_write(named_g_lctx,
-						      NAMED_LOGCATEGORY_GENERAL,
-						      NAMED_LOGMODULE_MAIN,
-						      ISC_LOG_CRITICAL, "%s",
-						      strs[i]);
-				}
-			}
-		}
+			      "%s:%d: %s(%s) failed", file, line,
+			      isc_assertion_typetotext(type), cond);
+		isc_backtrace_log(named_g_lctx, NAMED_LOGCATEGORY_GENERAL,
+				  NAMED_LOGMODULE_MAIN, ISC_LOG_CRITICAL);
 		isc_log_write(named_g_lctx, NAMED_LOGCATEGORY_GENERAL,
 			      NAMED_LOGMODULE_MAIN, ISC_LOG_CRITICAL,
 			      "exiting (due to assertion failure)");
diff --git a/lib/isc/assertions.c b/lib/isc/assertions.c
index a5cc0a2ac8..3dfccdcb07 100644
--- a/lib/isc/assertions.c
+++ b/lib/isc/assertions.c
@@ -95,8 +95,8 @@ isc_assertion_typetotext(isc_assertiontype_t type) {
 static void
 default_callback(const char *file, int line, isc_assertiontype_t type,
 		 const char *cond) {
-	void *tracebuf[BACKTRACE_MAXFRAME];
-	int nframes = isc_backtrace(tracebuf, BACKTRACE_MAXFRAME);
+	void *tracebuf[ISC_BACKTRACE_MAXFRAME];
+	int nframes = isc_backtrace(tracebuf, ISC_BACKTRACE_MAXFRAME);
 
 	fprintf(stderr, "%s:%d: %s(%s) failed%s\n", file, line,
 		isc_assertion_typetotext(type), cond,
diff --git a/lib/isc/backtrace.c b/lib/isc/backtrace.c
index fc15acf3eb..23369417fc 100644
--- a/lib/isc/backtrace.c
+++ b/lib/isc/backtrace.c
@@ -20,6 +20,7 @@
 #endif /* HAVE_BACKTRACE_SYMBOLS */
 
 #include <isc/backtrace.h>
+#include <isc/log.h>
 #include <isc/result.h>
 #include <isc/util.h>
 
@@ -60,6 +61,26 @@ isc_backtrace_symbols_fd(void *const *buffer, int size, int fd) {
 	backtrace_symbols_fd(buffer, size, fd);
 }
 
+void
+isc_backtrace_log(isc_log_t *lctx, isc_logcategory_t *category,
+		  isc_logmodule_t *module, int level) {
+	void *tracebuf[ISC_BACKTRACE_MAXFRAME];
+	int nframes;
+	char **strs;
+
+	nframes = isc_backtrace(tracebuf, ISC_BACKTRACE_MAXFRAME);
+	if (nframes <= 0) {
+		return;
+	}
+	strs = isc_backtrace_symbols(tracebuf, nframes);
+	if (strs == NULL) {
+		return;
+	}
+	for (int i = 0; i < nframes; i++) {
+		isc_log_write(lctx, category, module, level, "%s", strs[i]);
+	}
+}
+
 #else /* HAVE_BACKTRACE_SYMBOLS */
 
 int
@@ -85,4 +106,13 @@ isc_backtrace_symbols_fd(void *const *buffer, int size, int fd) {
 	UNUSED(fd);
 }
 
+void
+isc_backtrace_log(isc_log_t *lctx, isc_logcategory_t *category,
+		  isc_logmodule_t *module, int level) {
+	UNUSED(lctx);
+	UNUSED(category);
+	UNUSED(module);
+	UNUSED(level);
+}
+
 #endif /* HAVE_BACKTRACE_SYMBOLS */
diff --git a/lib/isc/include/isc/backtrace.h b/lib/isc/include/isc/backtrace.h
index f818c3b54a..c8fa3242b0 100644
--- a/lib/isc/include/isc/backtrace.h
+++ b/lib/isc/include/isc/backtrace.h
@@ -34,6 +34,13 @@
  ***/
 #include <isc/types.h>
 
+/*
+ * The maximum number of stack frames to dump on assertion failure.
+ */
+#ifndef ISC_BACKTRACE_MAXFRAME
+#define ISC_BACKTRACE_MAXFRAME 128
+#endif /* ifndef ISC_BACKTRACE_MAXFRAME */
+
 /***
  *** Functions
  ***/
@@ -98,4 +105,11 @@ isc_backtrace_symbols_fd(void *const *buffer, int size, int fd);
  *\li	See platform NOTES for backtrace_symbols_fd for caveats
  */
 
+void
+isc_backtrace_log(isc_log_t *lctx, isc_logcategory_t *category,
+		  isc_logmodule_t *module, int level);
+/*
+ * Write a backtrace to the log.
+ */
+
 ISC_LANG_ENDDECLS